The invention relates generally to internal combustion engines and to cooling systems therefor.
The invention relates more particularly to marine propulsion devices such as outboard motors and stern drive units, including internal combustion engines and cooling systems therefor.
Attention is directed to the Kueny U.S. Pat. No. 3,667,431 issued June 6, 1972 and to the Kueny et al U.S. Pat. No. 4,140,089 issued Feb. 20, 1979.
In the past, cooling systems of marine engines have included both a thermostatically controlled valve and a pressure actuated valve, often arranged in parallel, for controlling coolant flow from one portion of a coolant jacket to another. Such thermostatic valves opened upon the attainment of predetermined temperature conditions in the coolant and such pressure actuated valves opened upon the attainment of predetermined pressure conditions in the coolant. No arrangement was available for varying the levels of either the temperature or pressure at which the valves would open.